* AAC encoder psychoacoustic model
* Copyright (C) 2008 Konstantin Shishkov
*
- * This file is part of FFmpeg.
+ * This file is part of Libav.
*
- * FFmpeg is free software; you can redistribute it and/or
+ * Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
- * FFmpeg is distributed in the hope that it will be useful,
+ * Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
- * License along with FFmpeg; if not, write to the Free Software
+ * License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
- * @file libavcodec/aacpsy.c
+ * @file
* AAC encoder psychoacoustic model
*/
+#include "libavutil/attributes.h"
#include "avcodec.h"
-#include "aacpsy.h"
#include "aactab.h"
+#include "psymodel.h"
/***********************************
* TODOs:
- * General:
- * better audio preprocessing (add DC highpass filter?)
- * more psy models
- * maybe improve coefficient quantization function in some way
- *
- * 3GPP-based psy model:
- * thresholds linearization after their modifications for attaining given bitrate
* try other bitrate controlling mechanism (maybe use ratecontrol.c?)
* control quality for quality-based output
**********************************/
/**
- * Quantize one coefficient.
- * @return absolute value of the quantized coefficient
- * @see 3GPP TS26.403 5.6.2 "Scalefactor determination"
+ * constants for 3GPP AAC psychoacoustic model
+ * @{
+ */
+#define PSY_3GPP_THR_SPREAD_HI 1.5f // spreading factor for low-to-hi threshold spreading (15 dB/Bark)
+#define PSY_3GPP_THR_SPREAD_LOW 3.0f // spreading factor for hi-to-low threshold spreading (30 dB/Bark)
+/* spreading factor for low-to-hi energy spreading, long block, > 22kbps/channel (20dB/Bark) */
+#define PSY_3GPP_EN_SPREAD_HI_L1 2.0f
+/* spreading factor for low-to-hi energy spreading, long block, <= 22kbps/channel (15dB/Bark) */
+#define PSY_3GPP_EN_SPREAD_HI_L2 1.5f
+/* spreading factor for low-to-hi energy spreading, short block (15 dB/Bark) */
+#define PSY_3GPP_EN_SPREAD_HI_S 1.5f
+/* spreading factor for hi-to-low energy spreading, long block (30dB/Bark) */
+#define PSY_3GPP_EN_SPREAD_LOW_L 3.0f
+/* spreading factor for hi-to-low energy spreading, short block (20dB/Bark) */
+#define PSY_3GPP_EN_SPREAD_LOW_S 2.0f
+
+#define PSY_3GPP_RPEMIN 0.01f
+#define PSY_3GPP_RPELEV 2.0f
+
+#define PSY_3GPP_C1 3.0f /* log2(8) */
+#define PSY_3GPP_C2 1.3219281f /* log2(2.5) */
+#define PSY_3GPP_C3 0.55935729f /* 1 - C2 / C1 */
+
+#define PSY_SNR_1DB 7.9432821e-1f /* -1dB */
+#define PSY_SNR_25DB 3.1622776e-3f /* -25dB */
+
+#define PSY_3GPP_SAVE_SLOPE_L -0.46666667f
+#define PSY_3GPP_SAVE_SLOPE_S -0.36363637f
+#define PSY_3GPP_SAVE_ADD_L -0.84285712f
+#define PSY_3GPP_SAVE_ADD_S -0.75f
+#define PSY_3GPP_SPEND_SLOPE_L 0.66666669f
+#define PSY_3GPP_SPEND_SLOPE_S 0.81818181f
+#define PSY_3GPP_SPEND_ADD_L -0.35f
+#define PSY_3GPP_SPEND_ADD_S -0.26111111f
+#define PSY_3GPP_CLIP_LO_L 0.2f
+#define PSY_3GPP_CLIP_LO_S 0.2f
+#define PSY_3GPP_CLIP_HI_L 0.95f
+#define PSY_3GPP_CLIP_HI_S 0.75f
+
+#define PSY_3GPP_AH_THR_LONG 0.5f
+#define PSY_3GPP_AH_THR_SHORT 0.63f
+
+enum {
+ PSY_3GPP_AH_NONE,
+ PSY_3GPP_AH_INACTIVE,
+ PSY_3GPP_AH_ACTIVE
+};
+
+#define PSY_3GPP_BITS_TO_PE(bits) ((bits) * 1.18f)
+
+/* LAME psy model constants */
+#define PSY_LAME_FIR_LEN 21 ///< LAME psy model FIR order
+#define AAC_BLOCK_SIZE_LONG 1024 ///< long block size
+#define AAC_BLOCK_SIZE_SHORT 128 ///< short block size
+#define AAC_NUM_BLOCKS_SHORT 8 ///< number of blocks in a short sequence
+#define PSY_LAME_NUM_SUBBLOCKS 3 ///< Number of sub-blocks in each short block
+
+/**
+ * @}
+ */
+
+/**
+ * information for single band used by 3GPP TS26.403-inspired psychoacoustic model
+ */
+typedef struct AacPsyBand{
+ float energy; ///< band energy
+ float thr; ///< energy threshold
+ float thr_quiet; ///< threshold in quiet
+ float nz_lines; ///< number of non-zero spectral lines
+ float active_lines; ///< number of active spectral lines
+ float pe; ///< perceptual entropy
+ float pe_const; ///< constant part of the PE calculation
+ float norm_fac; ///< normalization factor for linearization
+ int avoid_holes; ///< hole avoidance flag
+}AacPsyBand;
+
+/**
+ * single/pair channel context for psychoacoustic model
+ */
+typedef struct AacPsyChannel{
+ AacPsyBand band[128]; ///< bands information
+ AacPsyBand prev_band[128]; ///< bands information from the previous frame
+
+ float win_energy; ///< sliding average of channel energy
+ float iir_state[2]; ///< hi-pass IIR filter state
+ uint8_t next_grouping; ///< stored grouping scheme for the next frame (in case of 8 short window sequence)
+ enum WindowSequence next_window_seq; ///< window sequence to be used in the next frame
+ /* LAME psy model specific members */
+ float attack_threshold; ///< attack threshold for this channel
+ float prev_energy_subshort[AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS];
+ int prev_attack; ///< attack value for the last short block in the previous sequence
+}AacPsyChannel;
+
+/**
+ * psychoacoustic model frame type-dependent coefficients
+ */
+typedef struct AacPsyCoeffs{
+ float ath; ///< absolute threshold of hearing per bands
+ float barks; ///< Bark value for each spectral band in long frame
+ float spread_low[2]; ///< spreading factor for low-to-high threshold spreading in long frame
+ float spread_hi [2]; ///< spreading factor for high-to-low threshold spreading in long frame
+ float min_snr; ///< minimal SNR
+}AacPsyCoeffs;
+
+/**
+ * 3GPP TS26.403-inspired psychoacoustic model specific data
+ */
+typedef struct AacPsyContext{
+ int chan_bitrate; ///< bitrate per channel
+ int frame_bits; ///< average bits per frame
+ int fill_level; ///< bit reservoir fill level
+ struct {
+ float min; ///< minimum allowed PE for bit factor calculation
+ float max; ///< maximum allowed PE for bit factor calculation
+ float previous; ///< allowed PE of the previous frame
+ float correction; ///< PE correction factor
+ } pe;
+ AacPsyCoeffs psy_coef[2][64];
+ AacPsyChannel *ch;
+}AacPsyContext;
+
+/**
+ * LAME psy model preset struct
+ */
+typedef struct {
+ int quality; ///< Quality to map the rest of the vaules to.
+ /* This is overloaded to be both kbps per channel in ABR mode, and
+ * requested quality in constant quality mode.
+ */
+ float st_lrm; ///< short threshold for L, R, and M channels
+} PsyLamePreset;
+
+/**
+ * LAME psy model preset table for ABR
+ */
+static const PsyLamePreset psy_abr_map[] = {
+/* TODO: Tuning. These were taken from LAME. */
+/* kbps/ch st_lrm */
+ { 8, 6.60},
+ { 16, 6.60},
+ { 24, 6.60},
+ { 32, 6.60},
+ { 40, 6.60},
+ { 48, 6.60},
+ { 56, 6.60},
+ { 64, 6.40},
+ { 80, 6.00},
+ { 96, 5.60},
+ {112, 5.20},
+ {128, 5.20},
+ {160, 5.20}
+};
+
+/**
+* LAME psy model preset table for constant quality
+*/
+static const PsyLamePreset psy_vbr_map[] = {
+/* vbr_q st_lrm */
+ { 0, 4.20},
+ { 1, 4.20},
+ { 2, 4.20},
+ { 3, 4.20},
+ { 4, 4.20},
+ { 5, 4.20},
+ { 6, 4.20},
+ { 7, 4.20},
+ { 8, 4.20},
+ { 9, 4.20},
+ {10, 4.20}
+};
+
+/**
+ * LAME psy model FIR coefficient table
+ */
+static const float psy_fir_coeffs[] = {
+ -8.65163e-18 * 2, -0.00851586 * 2, -6.74764e-18 * 2, 0.0209036 * 2,
+ -3.36639e-17 * 2, -0.0438162 * 2, -1.54175e-17 * 2, 0.0931738 * 2,
+ -5.52212e-17 * 2, -0.313819 * 2
+};
+
+/**
+ * Calculate the ABR attack threshold from the above LAME psymodel table.
*/
-static av_always_inline int quant(float coef, const float Q)
+static float lame_calc_attack_threshold(int bitrate)
{
- return av_clip((int)(pow(fabsf(coef) * Q, 0.75) + 0.4054), 0, 8191);
+ /* Assume max bitrate to start with */
+ int lower_range = 12, upper_range = 12;
+ int lower_range_kbps = psy_abr_map[12].quality;
+ int upper_range_kbps = psy_abr_map[12].quality;
+ int i;
+
+ /* Determine which bitrates the value specified falls between.
+ * If the loop ends without breaking our above assumption of 320kbps was correct.
+ */
+ for (i = 1; i < 13; i++) {
+ if (FFMAX(bitrate, psy_abr_map[i].quality) != bitrate) {
+ upper_range = i;
+ upper_range_kbps = psy_abr_map[i ].quality;
+ lower_range = i - 1;
+ lower_range_kbps = psy_abr_map[i - 1].quality;
+ break; /* Upper range found */
+ }
+ }
+
+ /* Determine which range the value specified is closer to */
+ if ((upper_range_kbps - bitrate) > (bitrate - lower_range_kbps))
+ return psy_abr_map[lower_range].st_lrm;
+ return psy_abr_map[upper_range].st_lrm;
}
-static inline float get_approximate_quant_error(float *c, int size, int scale_idx)
+/**
+ * LAME psy model specific initialization
+ */
+static av_cold void lame_window_init(AacPsyContext *ctx, AVCodecContext *avctx)
{
- int i;
- int q;
- float coef, unquant, sum = 0.0f;
- const float Q = ff_aac_pow2sf_tab[200 - scale_idx + SCALE_ONE_POS - SCALE_DIV_512];
- const float IQ = ff_aac_pow2sf_tab[200 + scale_idx - SCALE_ONE_POS + SCALE_DIV_512];
- for(i = 0; i < size; i++){
- coef = fabs(c[i]);
- q = quant(c[i], Q);
- unquant = (q * cbrt(q)) * IQ;
- sum += (coef - unquant) * (coef - unquant);
+ int i, j;
+
+ for (i = 0; i < avctx->channels; i++) {
+ AacPsyChannel *pch = &ctx->ch[i];
+
+ if (avctx->flags & CODEC_FLAG_QSCALE)
+ pch->attack_threshold = psy_vbr_map[avctx->global_quality / FF_QP2LAMBDA].st_lrm;
+ else
+ pch->attack_threshold = lame_calc_attack_threshold(avctx->bit_rate / avctx->channels / 1000);
+
+ for (j = 0; j < AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS; j++)
+ pch->prev_energy_subshort[j] = 10.0f;
}
- return sum;
}
/**
- * constants for 3GPP AAC psychoacoustic model
- * @{
+ * Calculate Bark value for given line.
*/
-#define PSY_3GPP_SPREAD_LOW 1.5f // spreading factor for ascending threshold spreading (15 dB/Bark)
-#define PSY_3GPP_SPREAD_HI 3.0f // spreading factor for descending threshold spreading (30 dB/Bark)
+static av_cold float calc_bark(float f)
+{
+ return 13.3f * atanf(0.00076f * f) + 3.5f * atanf((f / 7500.0f) * (f / 7500.0f));
+}
+
+#define ATH_ADD 4
/**
- * @}
+ * Calculate ATH value for given frequency.
+ * Borrowed from Lame.
*/
+static av_cold float ath(float f, float add)
+{
+ f /= 1000.0f;
+ return 3.64 * pow(f, -0.8)
+ - 6.8 * exp(-0.6 * (f - 3.4) * (f - 3.4))
+ + 6.0 * exp(-0.15 * (f - 8.7) * (f - 8.7))
+ + (0.6 + 0.04 * add) * 0.001 * f * f * f * f;
+}
+
+static av_cold int psy_3gpp_init(FFPsyContext *ctx) {
+ AacPsyContext *pctx;
+ float bark;
+ int i, j, g, start;
+ float prev, minscale, minath, minsnr, pe_min;
+ const int chan_bitrate = ctx->avctx->bit_rate / ctx->avctx->channels;
+ const int bandwidth = ctx->avctx->cutoff ? ctx->avctx->cutoff : ctx->avctx->sample_rate / 2;
+ const float num_bark = calc_bark((float)bandwidth);
+
+ ctx->model_priv_data = av_mallocz(sizeof(AacPsyContext));
+ pctx = (AacPsyContext*) ctx->model_priv_data;
+
+ pctx->chan_bitrate = chan_bitrate;
+ pctx->frame_bits = chan_bitrate * AAC_BLOCK_SIZE_LONG / ctx->avctx->sample_rate;
+ pctx->pe.min = 8.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f);
+ pctx->pe.max = 12.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f);
+ ctx->bitres.size = 6144 - pctx->frame_bits;
+ ctx->bitres.size -= ctx->bitres.size % 8;
+ pctx->fill_level = ctx->bitres.size;
+ minath = ath(3410, ATH_ADD);
+ for (j = 0; j < 2; j++) {
+ AacPsyCoeffs *coeffs = pctx->psy_coef[j];
+ const uint8_t *band_sizes = ctx->bands[j];
+ float line_to_frequency = ctx->avctx->sample_rate / (j ? 256.f : 2048.0f);
+ float avg_chan_bits = chan_bitrate * (j ? 128.0f : 1024.0f) / ctx->avctx->sample_rate;
+ /* reference encoder uses 2.4% here instead of 60% like the spec says */
+ float bark_pe = 0.024f * PSY_3GPP_BITS_TO_PE(avg_chan_bits) / num_bark;
+ float en_spread_low = j ? PSY_3GPP_EN_SPREAD_LOW_S : PSY_3GPP_EN_SPREAD_LOW_L;
+ /* High energy spreading for long blocks <= 22kbps/channel and short blocks are the same. */
+ float en_spread_hi = (j || (chan_bitrate <= 22.0f)) ? PSY_3GPP_EN_SPREAD_HI_S : PSY_3GPP_EN_SPREAD_HI_L1;
+
+ i = 0;
+ prev = 0.0;
+ for (g = 0; g < ctx->num_bands[j]; g++) {
+ i += band_sizes[g];
+ bark = calc_bark((i-1) * line_to_frequency);
+ coeffs[g].barks = (bark + prev) / 2.0;
+ prev = bark;
+ }
+ for (g = 0; g < ctx->num_bands[j] - 1; g++) {
+ AacPsyCoeffs *coeff = &coeffs[g];
+ float bark_width = coeffs[g+1].barks - coeffs->barks;
+ coeff->spread_low[0] = pow(10.0, -bark_width * PSY_3GPP_THR_SPREAD_LOW);
+ coeff->spread_hi [0] = pow(10.0, -bark_width * PSY_3GPP_THR_SPREAD_HI);
+ coeff->spread_low[1] = pow(10.0, -bark_width * en_spread_low);
+ coeff->spread_hi [1] = pow(10.0, -bark_width * en_spread_hi);
+ pe_min = bark_pe * bark_width;
+ minsnr = pow(2.0f, pe_min / band_sizes[g]) - 1.5f;
+ coeff->min_snr = av_clipf(1.0f / minsnr, PSY_SNR_25DB, PSY_SNR_1DB);
+ }
+ start = 0;
+ for (g = 0; g < ctx->num_bands[j]; g++) {
+ minscale = ath(start * line_to_frequency, ATH_ADD);
+ for (i = 1; i < band_sizes[g]; i++)
+ minscale = FFMIN(minscale, ath((start + i) * line_to_frequency, ATH_ADD));
+ coeffs[g].ath = minscale - minath;
+ start += band_sizes[g];
+ }
+ }
+
+ pctx->ch = av_mallocz(sizeof(AacPsyChannel) * ctx->avctx->channels);
+
+ lame_window_init(pctx, ctx->avctx);
+
+ return 0;
+}
/**
- * information for single band used by 3GPP TS26.403-inspired psychoacoustic model
+ * IIR filter used in block switching decision
*/
-typedef struct Psy3gppBand{
- float energy; ///< band energy
- float ffac; ///< form factor
-}Psy3gppBand;
+static float iir_filter(int in, float state[2])
+{
+ float ret;
+
+ ret = 0.7548f * (in - state[0]) + 0.5095f * state[1];
+ state[0] = in;
+ state[1] = ret;
+ return ret;
+}
/**
- * psychoacoustic model frame type-dependent coefficients
+ * window grouping information stored as bits (0 - new group, 1 - group continues)
*/
-typedef struct Psy3gppCoeffs{
- float ath [64]; ///< absolute threshold of hearing per bands
- float barks [64]; ///< Bark value for each spectral band in long frame
- float spread_low[64]; ///< spreading factor for low-to-high threshold spreading in long frame
- float spread_hi [64]; ///< spreading factor for high-to-low threshold spreading in long frame
-}Psy3gppCoeffs;
+static const uint8_t window_grouping[9] = {
+ 0xB6, 0x6C, 0xD8, 0xB2, 0x66, 0xC6, 0x96, 0x36, 0x36
+};
/**
- * Calculate Bark value for given line.
+ * Tell encoder which window types to use.
+ * @see 3GPP TS26.403 5.4.1 "Blockswitching"
*/
-static inline float calc_bark(float f)
+static av_unused FFPsyWindowInfo psy_3gpp_window(FFPsyContext *ctx,
+ const int16_t *audio,
+ const int16_t *la,
+ int channel, int prev_type)
{
- return 13.3f * atanf(0.00076f * f) + 3.5f * atanf((f / 7500.0f) * (f / 7500.0f));
+ int i, j;
+ int br = ctx->avctx->bit_rate / ctx->avctx->channels;
+ int attack_ratio = br <= 16000 ? 18 : 10;
+ AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
+ AacPsyChannel *pch = &pctx->ch[channel];
+ uint8_t grouping = 0;
+ int next_type = pch->next_window_seq;
+ FFPsyWindowInfo wi = { { 0 } };
+
+ if (la) {
+ float s[8], v;
+ int switch_to_eight = 0;
+ float sum = 0.0, sum2 = 0.0;
+ int attack_n = 0;
+ int stay_short = 0;
+ for (i = 0; i < 8; i++) {
+ for (j = 0; j < 128; j++) {
+ v = iir_filter(la[i*128+j], pch->iir_state);
+ sum += v*v;
+ }
+ s[i] = sum;
+ sum2 += sum;
+ }
+ for (i = 0; i < 8; i++) {
+ if (s[i] > pch->win_energy * attack_ratio) {
+ attack_n = i + 1;
+ switch_to_eight = 1;
+ break;
+ }
+ }
+ pch->win_energy = pch->win_energy*7/8 + sum2/64;
+
+ wi.window_type[1] = prev_type;
+ switch (prev_type) {
+ case ONLY_LONG_SEQUENCE:
+ wi.window_type[0] = switch_to_eight ? LONG_START_SEQUENCE : ONLY_LONG_SEQUENCE;
+ next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : ONLY_LONG_SEQUENCE;
+ break;
+ case LONG_START_SEQUENCE:
+ wi.window_type[0] = EIGHT_SHORT_SEQUENCE;
+ grouping = pch->next_grouping;
+ next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
+ break;
+ case LONG_STOP_SEQUENCE:
+ wi.window_type[0] = switch_to_eight ? LONG_START_SEQUENCE : ONLY_LONG_SEQUENCE;
+ next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : ONLY_LONG_SEQUENCE;
+ break;
+ case EIGHT_SHORT_SEQUENCE:
+ stay_short = next_type == EIGHT_SHORT_SEQUENCE || switch_to_eight;
+ wi.window_type[0] = stay_short ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
+ grouping = next_type == EIGHT_SHORT_SEQUENCE ? pch->next_grouping : 0;
+ next_type = switch_to_eight ? EIGHT_SHORT_SEQUENCE : LONG_STOP_SEQUENCE;
+ break;
+ }
+
+ pch->next_grouping = window_grouping[attack_n];
+ pch->next_window_seq = next_type;
+ } else {
+ for (i = 0; i < 3; i++)
+ wi.window_type[i] = prev_type;
+ grouping = (prev_type == EIGHT_SHORT_SEQUENCE) ? window_grouping[0] : 0;
+ }
+
+ wi.window_shape = 1;
+ if (wi.window_type[0] != EIGHT_SHORT_SEQUENCE) {
+ wi.num_windows = 1;
+ wi.grouping[0] = 1;
+ } else {
+ int lastgrp = 0;
+ wi.num_windows = 8;
+ for (i = 0; i < 8; i++) {
+ if (!((grouping >> i) & 1))
+ lastgrp = i;
+ wi.grouping[lastgrp]++;
+ }
+ }
+
+ return wi;
}
+
+/* 5.6.1.2 "Calculation of Bit Demand" */
+static int calc_bit_demand(AacPsyContext *ctx, float pe, int bits, int size,
+ int short_window)
+{
+ const float bitsave_slope = short_window ? PSY_3GPP_SAVE_SLOPE_S : PSY_3GPP_SAVE_SLOPE_L;
+ const float bitsave_add = short_window ? PSY_3GPP_SAVE_ADD_S : PSY_3GPP_SAVE_ADD_L;
+ const float bitspend_slope = short_window ? PSY_3GPP_SPEND_SLOPE_S : PSY_3GPP_SPEND_SLOPE_L;
+ const float bitspend_add = short_window ? PSY_3GPP_SPEND_ADD_S : PSY_3GPP_SPEND_ADD_L;
+ const float clip_low = short_window ? PSY_3GPP_CLIP_LO_S : PSY_3GPP_CLIP_LO_L;
+ const float clip_high = short_window ? PSY_3GPP_CLIP_HI_S : PSY_3GPP_CLIP_HI_L;
+ float clipped_pe, bit_save, bit_spend, bit_factor, fill_level;
+
+ ctx->fill_level += ctx->frame_bits - bits;
+ ctx->fill_level = av_clip(ctx->fill_level, 0, size);
+ fill_level = av_clipf((float)ctx->fill_level / size, clip_low, clip_high);
+ clipped_pe = av_clipf(pe, ctx->pe.min, ctx->pe.max);
+ bit_save = (fill_level + bitsave_add) * bitsave_slope;
+ assert(bit_save <= 0.3f && bit_save >= -0.05000001f);
+ bit_spend = (fill_level + bitspend_add) * bitspend_slope;
+ assert(bit_spend <= 0.5f && bit_spend >= -0.1f);
+ /* The bit factor graph in the spec is obviously incorrect.
+ * bit_spend + ((bit_spend - bit_spend))...
+ * The reference encoder subtracts everything from 1, but also seems incorrect.
+ * 1 - bit_save + ((bit_spend + bit_save))...
+ * Hopefully below is correct.
+ */
+ bit_factor = 1.0f - bit_save + ((bit_spend - bit_save) / (ctx->pe.max - ctx->pe.min)) * (clipped_pe - ctx->pe.min);
+ /* NOTE: The reference encoder attempts to center pe max/min around the current pe. */
+ ctx->pe.max = FFMAX(pe, ctx->pe.max);
+ ctx->pe.min = FFMIN(pe, ctx->pe.min);
+
+ return FFMIN(ctx->frame_bits * bit_factor, ctx->frame_bits + size - bits);
+}
+
+static float calc_pe_3gpp(AacPsyBand *band)
+{
+ float pe, a;
+
+ band->pe = 0.0f;
+ band->pe_const = 0.0f;
+ band->active_lines = 0.0f;
+ if (band->energy > band->thr) {
+ a = log2f(band->energy);
+ pe = a - log2f(band->thr);
+ band->active_lines = band->nz_lines;
+ if (pe < PSY_3GPP_C1) {
+ pe = pe * PSY_3GPP_C3 + PSY_3GPP_C2;
+ a = a * PSY_3GPP_C3 + PSY_3GPP_C2;
+ band->active_lines *= PSY_3GPP_C3;
+ }
+ band->pe = pe * band->nz_lines;
+ band->pe_const = a * band->nz_lines;
+ }
+
+ return band->pe;
+}
+
+static float calc_reduction_3gpp(float a, float desired_pe, float pe,
+ float active_lines)
+{
+ float thr_avg, reduction;
+
+ thr_avg = powf(2.0f, (a - pe) / (4.0f * active_lines));
+ reduction = powf(2.0f, (a - desired_pe) / (4.0f * active_lines)) - thr_avg;
+
+ return FFMAX(reduction, 0.0f);
+}
+
+static float calc_reduced_thr_3gpp(AacPsyBand *band, float min_snr,
+ float reduction)
+{
+ float thr = band->thr;
+
+ if (band->energy > thr) {
+ thr = powf(thr, 0.25f) + reduction;
+ thr = powf(thr, 4.0f);
+
+ /* This deviates from the 3GPP spec to match the reference encoder.
+ * It performs min(thr_reduced, max(thr, energy/min_snr)) only for bands
+ * that have hole avoidance on (active or inactive). It always reduces the
+ * threshold of bands with hole avoidance off.
+ */
+ if (thr > band->energy * min_snr && band->avoid_holes != PSY_3GPP_AH_NONE) {
+ thr = FFMAX(band->thr, band->energy * min_snr);
+ band->avoid_holes = PSY_3GPP_AH_ACTIVE;
+ }
+ }
+
+ return thr;
+}
+
+/**
+ * Calculate band thresholds as suggested in 3GPP TS26.403
+ */
+static void psy_3gpp_analyze_channel(FFPsyContext *ctx, int channel,
+ const float *coefs, const FFPsyWindowInfo *wi)
+{
+ AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
+ AacPsyChannel *pch = &pctx->ch[channel];
+ int start = 0;
+ int i, w, g;
+ float desired_bits, desired_pe, delta_pe, reduction, spread_en[128] = {0};
+ float a = 0.0f, active_lines = 0.0f, norm_fac = 0.0f;
+ float pe = pctx->chan_bitrate > 32000 ? 0.0f : FFMAX(50.0f, 100.0f - pctx->chan_bitrate * 100.0f / 32000.0f);
+ const int num_bands = ctx->num_bands[wi->num_windows == 8];
+ const uint8_t *band_sizes = ctx->bands[wi->num_windows == 8];
+ AacPsyCoeffs *coeffs = pctx->psy_coef[wi->num_windows == 8];
+ const float avoid_hole_thr = wi->num_windows == 8 ? PSY_3GPP_AH_THR_SHORT : PSY_3GPP_AH_THR_LONG;
+
+ //calculate energies, initial thresholds and related values - 5.4.2 "Threshold Calculation"
+ for (w = 0; w < wi->num_windows*16; w += 16) {
+ for (g = 0; g < num_bands; g++) {
+ AacPsyBand *band = &pch->band[w+g];
+
+ float form_factor = 0.0f;
+ band->energy = 0.0f;
+ for (i = 0; i < band_sizes[g]; i++) {
+ band->energy += coefs[start+i] * coefs[start+i];
+ form_factor += sqrtf(fabs(coefs[start+i]));
+ }
+ band->thr = band->energy * 0.001258925f;
+ band->nz_lines = form_factor / powf(band->energy / band_sizes[g], 0.25f);
+
+ start += band_sizes[g];
+ }
+ }
+ //modify thresholds and energies - spread, threshold in quiet, pre-echo control
+ for (w = 0; w < wi->num_windows*16; w += 16) {
+ AacPsyBand *bands = &pch->band[w];
+
+ /* 5.4.2.3 "Spreading" & 5.4.3 "Spread Energy Calculation" */
+ spread_en[0] = bands[0].energy;
+ for (g = 1; g < num_bands; g++) {
+ bands[g].thr = FFMAX(bands[g].thr, bands[g-1].thr * coeffs[g].spread_hi[0]);
+ spread_en[w+g] = FFMAX(bands[g].energy, spread_en[w+g-1] * coeffs[g].spread_hi[1]);
+ }
+ for (g = num_bands - 2; g >= 0; g--) {
+ bands[g].thr = FFMAX(bands[g].thr, bands[g+1].thr * coeffs[g].spread_low[0]);
+ spread_en[w+g] = FFMAX(spread_en[w+g], spread_en[w+g+1] * coeffs[g].spread_low[1]);
+ }
+ //5.4.2.4 "Threshold in quiet"
+ for (g = 0; g < num_bands; g++) {
+ AacPsyBand *band = &bands[g];
+
+ band->thr_quiet = band->thr = FFMAX(band->thr, coeffs[g].ath);
+ //5.4.2.5 "Pre-echo control"
+ if (!(wi->window_type[0] == LONG_STOP_SEQUENCE || (wi->window_type[1] == LONG_START_SEQUENCE && !w)))
+ band->thr = FFMAX(PSY_3GPP_RPEMIN*band->thr, FFMIN(band->thr,
+ PSY_3GPP_RPELEV*pch->prev_band[w+g].thr_quiet));
+
+ /* 5.6.1.3.1 "Preparatory steps of the perceptual entropy calculation" */
+ pe += calc_pe_3gpp(band);
+ a += band->pe_const;
+ active_lines += band->active_lines;
+
+ /* 5.6.1.3.3 "Selection of the bands for avoidance of holes" */
+ if (spread_en[w+g] * avoid_hole_thr > band->energy || coeffs[g].min_snr > 1.0f)
+ band->avoid_holes = PSY_3GPP_AH_NONE;
+ else
+ band->avoid_holes = PSY_3GPP_AH_INACTIVE;
+ }
+ }
+
+ /* 5.6.1.3.2 "Calculation of the desired perceptual entropy" */
+ ctx->ch[channel].entropy = pe;
+ desired_bits = calc_bit_demand(pctx, pe, ctx->bitres.bits, ctx->bitres.size, wi->num_windows == 8);
+ desired_pe = PSY_3GPP_BITS_TO_PE(desired_bits);
+ /* NOTE: PE correction is kept simple. During initial testing it had very
+ * little effect on the final bitrate. Probably a good idea to come
+ * back and do more testing later.
+ */
+ if (ctx->bitres.bits > 0)
+ desired_pe *= av_clipf(pctx->pe.previous / PSY_3GPP_BITS_TO_PE(ctx->bitres.bits),
+ 0.85f, 1.15f);
+ pctx->pe.previous = PSY_3GPP_BITS_TO_PE(desired_bits);
+
+ if (desired_pe < pe) {
+ /* 5.6.1.3.4 "First Estimation of the reduction value" */
+ for (w = 0; w < wi->num_windows*16; w += 16) {
+ reduction = calc_reduction_3gpp(a, desired_pe, pe, active_lines);
+ pe = 0.0f;
+ a = 0.0f;
+ active_lines = 0.0f;
+ for (g = 0; g < num_bands; g++) {
+ AacPsyBand *band = &pch->band[w+g];
+
+ band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction);
+ /* recalculate PE */
+ pe += calc_pe_3gpp(band);
+ a += band->pe_const;
+ active_lines += band->active_lines;
+ }
+ }
+
+ /* 5.6.1.3.5 "Second Estimation of the reduction value" */
+ for (i = 0; i < 2; i++) {
+ float pe_no_ah = 0.0f, desired_pe_no_ah;
+ active_lines = a = 0.0f;
+ for (w = 0; w < wi->num_windows*16; w += 16) {
+ for (g = 0; g < num_bands; g++) {
+ AacPsyBand *band = &pch->band[w+g];
+
+ if (band->avoid_holes != PSY_3GPP_AH_ACTIVE) {
+ pe_no_ah += band->pe;
+ a += band->pe_const;
+ active_lines += band->active_lines;
+ }
+ }
+ }
+ desired_pe_no_ah = FFMAX(desired_pe - (pe - pe_no_ah), 0.0f);
+ if (active_lines > 0.0f)
+ reduction += calc_reduction_3gpp(a, desired_pe_no_ah, pe_no_ah, active_lines);
+
+ pe = 0.0f;
+ for (w = 0; w < wi->num_windows*16; w += 16) {
+ for (g = 0; g < num_bands; g++) {
+ AacPsyBand *band = &pch->band[w+g];
+
+ if (active_lines > 0.0f)
+ band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction);
+ pe += calc_pe_3gpp(band);
+ band->norm_fac = band->active_lines / band->thr;
+ norm_fac += band->norm_fac;
+ }
+ }
+ delta_pe = desired_pe - pe;
+ if (fabs(delta_pe) > 0.05f * desired_pe)
+ break;
+ }
+
+ if (pe < 1.15f * desired_pe) {
+ /* 6.6.1.3.6 "Final threshold modification by linearization" */
+ norm_fac = 1.0f / norm_fac;
+ for (w = 0; w < wi->num_windows*16; w += 16) {
+ for (g = 0; g < num_bands; g++) {
+ AacPsyBand *band = &pch->band[w+g];
+
+ if (band->active_lines > 0.5f) {
+ float delta_sfb_pe = band->norm_fac * norm_fac * delta_pe;
+ float thr = band->thr;
+
+ thr *= powf(2.0f, delta_sfb_pe / band->active_lines);
+ if (thr > coeffs[g].min_snr * band->energy && band->avoid_holes == PSY_3GPP_AH_INACTIVE)
+ thr = FFMAX(band->thr, coeffs[g].min_snr * band->energy);
+ band->thr = thr;
+ }
+ }
+ }
+ } else {
+ /* 5.6.1.3.7 "Further perceptual entropy reduction" */
+ g = num_bands;
+ while (pe > desired_pe && g--) {
+ for (w = 0; w < wi->num_windows*16; w+= 16) {
+ AacPsyBand *band = &pch->band[w+g];
+ if (band->avoid_holes != PSY_3GPP_AH_NONE && coeffs[g].min_snr < PSY_SNR_1DB) {
+ coeffs[g].min_snr = PSY_SNR_1DB;
+ band->thr = band->energy * PSY_SNR_1DB;
+ pe += band->active_lines * 1.5f - band->pe;
+ }
+ }
+ }
+ /* TODO: allow more holes (unused without mid/side) */
+ }
+ }
+
+ for (w = 0; w < wi->num_windows*16; w += 16) {
+ for (g = 0; g < num_bands; g++) {
+ AacPsyBand *band = &pch->band[w+g];
+ FFPsyBand *psy_band = &ctx->ch[channel].psy_bands[w+g];
+
+ psy_band->threshold = band->thr;
+ psy_band->energy = band->energy;
+ }
+ }
+
+ memcpy(pch->prev_band, pch->band, sizeof(pch->band));
+}
+
+static void psy_3gpp_analyze(FFPsyContext *ctx, int channel,
+ const float **coeffs, const FFPsyWindowInfo *wi)
+{
+ int ch;
+ FFPsyChannelGroup *group = ff_psy_find_group(ctx, channel);
+
+ for (ch = 0; ch < group->num_ch; ch++)
+ psy_3gpp_analyze_channel(ctx, channel + ch, coeffs[ch], &wi[ch]);
+}
+
+static av_cold void psy_3gpp_end(FFPsyContext *apc)
+{
+ AacPsyContext *pctx = (AacPsyContext*) apc->model_priv_data;
+ av_freep(&pctx->ch);
+ av_freep(&apc->model_priv_data);
+}
+
+static void lame_apply_block_type(AacPsyChannel *ctx, FFPsyWindowInfo *wi, int uselongblock)
+{
+ int blocktype = ONLY_LONG_SEQUENCE;
+ if (uselongblock) {
+ if (ctx->next_window_seq == EIGHT_SHORT_SEQUENCE)
+ blocktype = LONG_STOP_SEQUENCE;
+ } else {
+ blocktype = EIGHT_SHORT_SEQUENCE;
+ if (ctx->next_window_seq == ONLY_LONG_SEQUENCE)
+ ctx->next_window_seq = LONG_START_SEQUENCE;
+ if (ctx->next_window_seq == LONG_STOP_SEQUENCE)
+ ctx->next_window_seq = EIGHT_SHORT_SEQUENCE;
+ }
+
+ wi->window_type[0] = ctx->next_window_seq;
+ ctx->next_window_seq = blocktype;
+}
+
+static FFPsyWindowInfo psy_lame_window(FFPsyContext *ctx, const float *audio,
+ const float *la, int channel, int prev_type)
+{
+ AacPsyContext *pctx = (AacPsyContext*) ctx->model_priv_data;
+ AacPsyChannel *pch = &pctx->ch[channel];
+ int grouping = 0;
+ int uselongblock = 1;
+ int attacks[AAC_NUM_BLOCKS_SHORT + 1] = { 0 };
+ int i;
+ FFPsyWindowInfo wi = { { 0 } };
+
+ if (la) {
+ float hpfsmpl[AAC_BLOCK_SIZE_LONG];
+ float const *pf = hpfsmpl;
+ float attack_intensity[(AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS];
+ float energy_subshort[(AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS];
+ float energy_short[AAC_NUM_BLOCKS_SHORT + 1] = { 0 };
+ const float *firbuf = la + (AAC_BLOCK_SIZE_SHORT/4 - PSY_LAME_FIR_LEN);
+ int j, att_sum = 0;
+
+ /* LAME comment: apply high pass filter of fs/4 */
+ for (i = 0; i < AAC_BLOCK_SIZE_LONG; i++) {
+ float sum1, sum2;
+ sum1 = firbuf[i + (PSY_LAME_FIR_LEN - 1) / 2];
+ sum2 = 0.0;
+ for (j = 0; j < ((PSY_LAME_FIR_LEN - 1) / 2) - 1; j += 2) {
+ sum1 += psy_fir_coeffs[j] * (firbuf[i + j] + firbuf[i + PSY_LAME_FIR_LEN - j]);
+ sum2 += psy_fir_coeffs[j + 1] * (firbuf[i + j + 1] + firbuf[i + PSY_LAME_FIR_LEN - j - 1]);
+ }
+ /* NOTE: The LAME psymodel expects its input in the range -32768 to
+ * 32768. Tuning this for normalized floats would be difficult. */
+ hpfsmpl[i] = (sum1 + sum2) * 32768.0f;
+ }
+
+ /* Calculate the energies of each sub-shortblock */
+ for (i = 0; i < PSY_LAME_NUM_SUBBLOCKS; i++) {
+ energy_subshort[i] = pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 1) * PSY_LAME_NUM_SUBBLOCKS)];
+ assert(pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 2) * PSY_LAME_NUM_SUBBLOCKS + 1)] > 0);
+ attack_intensity[i] = energy_subshort[i] / pch->prev_energy_subshort[i + ((AAC_NUM_BLOCKS_SHORT - 2) * PSY_LAME_NUM_SUBBLOCKS + 1)];
+ energy_short[0] += energy_subshort[i];
+ }
+
+ for (i = 0; i < AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS; i++) {
+ float const *const pfe = pf + AAC_BLOCK_SIZE_LONG / (AAC_NUM_BLOCKS_SHORT * PSY_LAME_NUM_SUBBLOCKS);
+ float p = 1.0f;
+ for (; pf < pfe; pf++)
+ p = FFMAX(p, fabsf(*pf));
+ pch->prev_energy_subshort[i] = energy_subshort[i + PSY_LAME_NUM_SUBBLOCKS] = p;
+ energy_short[1 + i / PSY_LAME_NUM_SUBBLOCKS] += p;
+ /* NOTE: The indexes below are [i + 3 - 2] in the LAME source.
+ * Obviously the 3 and 2 have some significance, or this would be just [i + 1]
+ * (which is what we use here). What the 3 stands for is ambiguous, as it is both
+ * number of short blocks, and the number of sub-short blocks.
+ * It seems that LAME is comparing each sub-block to sub-block + 1 in the
+ * previous block.
+ */
+ if (p > energy_subshort[i + 1])
+ p = p / energy_subshort[i + 1];
+ else if (energy_subshort[i + 1] > p * 10.0f)
+ p = energy_subshort[i + 1] / (p * 10.0f);
+ else
+ p = 0.0;
+ attack_intensity[i + PSY_LAME_NUM_SUBBLOCKS] = p;
+ }
+
+ /* compare energy between sub-short blocks */
+ for (i = 0; i < (AAC_NUM_BLOCKS_SHORT + 1) * PSY_LAME_NUM_SUBBLOCKS; i++)
+ if (!attacks[i / PSY_LAME_NUM_SUBBLOCKS])
+ if (attack_intensity[i] > pch->attack_threshold)
+ attacks[i / PSY_LAME_NUM_SUBBLOCKS] = (i % PSY_LAME_NUM_SUBBLOCKS) + 1;
+
+ /* should have energy change between short blocks, in order to avoid periodic signals */
+ /* Good samples to show the effect are Trumpet test songs */
+ /* GB: tuned (1) to avoid too many short blocks for test sample TRUMPET */
+ /* RH: tuned (2) to let enough short blocks through for test sample FSOL and SNAPS */
+ for (i = 1; i < AAC_NUM_BLOCKS_SHORT + 1; i++) {
+ float const u = energy_short[i - 1];
+ float const v = energy_short[i];
+ float const m = FFMAX(u, v);
+ if (m < 40000) { /* (2) */
+ if (u < 1.7f * v && v < 1.7f * u) { /* (1) */
+ if (i == 1 && attacks[0] < attacks[i])
+ attacks[0] = 0;
+ attacks[i] = 0;
+ }
+ }
+ att_sum += attacks[i];
+ }
+
+ if (attacks[0] <= pch->prev_attack)
+ attacks[0] = 0;
+
+ att_sum += attacks[0];
+ /* 3 below indicates the previous attack happened in the last sub-block of the previous sequence */
+ if (pch->prev_attack == 3 || att_sum) {
+ uselongblock = 0;
+
+ for (i = 1; i < AAC_NUM_BLOCKS_SHORT + 1; i++)
+ if (attacks[i] && attacks[i-1])
+ attacks[i] = 0;
+ }
+ } else {
+ /* We have no lookahead info, so just use same type as the previous sequence. */
+ uselongblock = !(prev_type == EIGHT_SHORT_SEQUENCE);
+ }
+
+ lame_apply_block_type(pch, &wi, uselongblock);
+
+ wi.window_type[1] = prev_type;
+ if (wi.window_type[0] != EIGHT_SHORT_SEQUENCE) {
+ wi.num_windows = 1;
+ wi.grouping[0] = 1;
+ if (wi.window_type[0] == LONG_START_SEQUENCE)
+ wi.window_shape = 0;
+ else
+ wi.window_shape = 1;
+ } else {
+ int lastgrp = 0;
+
+ wi.num_windows = 8;
+ wi.window_shape = 0;
+ for (i = 0; i < 8; i++) {
+ if (!((pch->next_grouping >> i) & 1))
+ lastgrp = i;
+ wi.grouping[lastgrp]++;
+ }
+ }
+
+ /* Determine grouping, based on the location of the first attack, and save for
+ * the next frame.
+ * FIXME: Move this to analysis.
+ * TODO: Tune groupings depending on attack location
+ * TODO: Handle more than one attack in a group
+ */
+ for (i = 0; i < 9; i++) {
+ if (attacks[i]) {
+ grouping = i;
+ break;
+ }
+ }
+ pch->next_grouping = window_grouping[grouping];
+
+ pch->prev_attack = attacks[8];
+
+ return wi;
+}
+
+const FFPsyModel ff_aac_psy_model =
+{
+ .name = "3GPP TS 26.403-inspired model",
+ .init = psy_3gpp_init,
+ .window = psy_lame_window,
+ .analyze = psy_3gpp_analyze,
+ .end = psy_3gpp_end,
+};